1. Field of the Invention
The present invention relates to a computer program product, system, and method for replicating tracks from a first storage to a second and third storages.
2. Description of the Related Art
In a storage environment, volumes may be mirrored to other volumes to provide redundant copies of data. A point-in-time copy replicates data in a manner that appears instantaneous and allows a host to continue accessing the source volume while actual data transfers to the copy volume are deferred to a later time. The point-in-time copy appears instantaneous because complete is returned to the copy operation in response to generating the relationship data structures without copying the data. Point-in-time copy techniques, such as the IBM FlashCopy® (FlashCopy is a registered trademark of International Business Machines, Corp. or “IBM”), defer the transfer of data back to the copy volume until a write operation is requested to that data block on the source volume. The FlashCopy operation may specify a background copy operation to copy tracks subject to the FlashCopy relation in the background before a write is received. Until the actual copy operation occurs, reads are directed to the data blocks on the source volume. The point-in-time copy relationships that are immediately established in response to the point-in-time copy command include a bitmap or other data structure indicating the location of blocks in the volume at either the source volume or the copy volume.
The FlashCopy relationship may also be configured with no background copy, so that tracks are only copied before a write is applied to the track. In this configuration, when a track is destaged on the source, the previous version of the source on the disk may need to be copied to the target before the destage is allowed on the source. This is done using a CST (Copy Source to Target) operation. CST will stage the track from the source disk and then synthesize the target track in the target cache and then destage the track to the target storage. Once the destage on the target is complete, the track is demoted from cache in an accelerated fashion.
In further configurations, the FlashCopy target may also comprise a primary storage in a mirror Peer-to-Peer Copy (PPRC) relationship. In such a case, the track in the PPRC primary, which is also the FlashCopy target, may need to be transferred to the PPRC secondary storage in a PPRC remote site.
There is a need in the art for improved techniques for managing the replication of a track in a first storage to multiple replication storages.